A suicide car bomber targeted a U.S. consulate vehicle in Pakistan Monday, in an attack officials said killed four, but there were conflicting accounts of whether Americans were among the dead.

The bomber struck during the morning rush hour, close to residential quarters used by the US consulate in the northwestern city of Peshawar and near the office of the UN Refugee Agency (UNHCR).

Although the identities of the victims were unclear, it was the deadliest attack in two years targeting Americans in Pakistan, a frontline state in the US-led war on terror and the fight against the Taliban in neighboring Afghanistan.

Mian Iftikhar Hussain, information minister for Khyber Pakhtunkhwa province, said four people were killed in the suicide attack, two of them Americans.